The present invention may be used in conjunction with a variety of items often found in a supply stream such as, for example, food products, building components, and manufacturing components. However, the present application is particularly useful with preforms. Preforms are typically formed of a thermoplastic and are the initial material for thinwall containers such as bottles for soft drinks, detergents, etc. produced with blow molding machines.
In one method of blow molding plastic containers, such as polyethylene terephthalate (PET) carbonated beverage bottles, a preform first is formed by injection molding followed by reheating and stretch blow molding of such preforms into a container. The preforms are generally cylindrical tubes having a hemispherical closed end and an opposite, open end having a ring shaped shoulder and threaded sleeve. Superficially, preforms generally resemble test tubes having a threaded end.
Depending upon the size of the container to be blow formed, the preforms have different sizes, particularly in length and wall thickness, whereas the thread diameters are somewhat standardized with reference diameters being 22, 28, and 38 mm, measured on the outside of the thread.
The preforms are injection molded in large numbers at an injection molding machine, which includes a preform handling or cooling plate. After the preforms are removed from the injection molding machine, they are brought to an elevated position by a conveyor belt and then delivered by a chute to a large corrugated cardboard, plastic, or steel box normally identified as a “gaylord” for storage and shipment. The preforms merely drop from the chute into the gaylord. Since the gaylord may be four or more feet tall and the chute discharge is at a still higher elevation, a drop from the chute to the bottom of the gaylord may be 5 feet or more.
Surface damage to the preform typically occurs during dropping through such distances into the gaylord. Such damage is manifested by scratching or scuffing of the surface of the preform, or, and in an extreme case, in the chipping of a threaded surface. Since this damage occurs during loading of the articles, which is generally after inspection, the damage often goes undetected. Consequently, such defects on the exterior surface of a preform result in a blow molded container having an unacceptable surface contusion. Such containers generally are not fit for sale and must be discarded, as consumers prefer not to purchase damaged products.
A number of methods have been applied to reduce the surface damage to preforms prior to the final blow molding process. Specifically, U.S. Pat. No. 5,509,965 discloses immediately coating preforms after injection molding of such preforms to prevent damage of the preforms by engagement with one another. However, this process, like many other processes used heretofore, typically requires additional materials and processing equipment, thereby adding to the cost of forming and handling the preforms.
U.S. Pat. No. 6,637,480 provides another method for handling performs. Namely, that patent discloses a variable volume height adjustable buffer for transferring items from an elevated supply stream to a lower container. The '480 patent is assigned to the same assignee as this application, and the apparatus and methods disclosed therein are effective at filling gaylords with provided preforms by using an expandable buffer.
However, there remains a need in the art for a system that can transfer, with minimal or no damage, preforms from the injection mold supply stream into relatively lower containers for storage and transport.
There also is a need in the art for a system for loading a multitude of similar articles into relatively deep containers that minimizes damage to the articles particularly where the articles are dropped from a relatively high elevation relative to the bottom of the container.
There also is a need for such a system for loading a multitude of similar articles into a deep container wherein the drop or fall distance into the container is kept relatively constant regardless of the container height.
There also is a need for a system for loading a multitude of similar articles into a deep container wherein the articles are distributed relatively evenly throughout the container, to minimize localized piling of the articles.